The overall objectives of this project continue to be the elucidation of mechanisms which serve to coordinate visceral smooth muscle activity. Our efforts during the next granting period will be directed toward: a) Studying the effects of estrogen and progesterone on the electrical activity, inter-cellular electrical coupling, and mechanical properties of non-uterine visceral smooth muscle, especially that of the gastrointestinal tract, in chronic animal preparations and in vitro; b) Studying the changes in electrical and mechanical activity accompanying hypertrophy of intestinal muscle associated with pressure overload caused by chronic obstruction, or volume overload caused by extensive intestinal resection, especially of the upper small bowel. These studies will be performed on chronic dog and cat preparations and on isolated smooth muscle preparations.